While the insertion of nonlocal descriptors in classical differential formulations of continuum mechanics (as strain gradient, convolution kernels, etc.) has a long tradition ([1]}, [2]}, [3]}, [4]}, [5]}, [6]}), the acceptance ab initio of a material intrinsic length-scale in a genuinely nonlocal theory is a more recent achievement and peridynamics, as initiated by S.A. Silling (see [7]}, [8]}, [9]}, [10]}, [11]}), seems to have good chances
to shed some new light on these problems.
